Thermostatic valve for a cooling circuit

ABSTRACT

This valve comprises a housing, a movable check mechanism that is suitable for regulating the passage of a fluid between an inlet orifice and an outlet orifice of the housing, a stationary seat for receiving the valve, and a thermostatic element that is provided with a body, which contains an expandable material, and a movable piston, this body being stationary relative to the housing. In order to prevent excessive pressure from being generated in the valve, on the side of the check mechanism where the thermostatic element is arranged, the check mechanism and the piston are connected by a part that is integral with the valve and delimits a blind recess for receiving the piston, the base of the recess forming a stop for the piston when the difference in pressure on either side of the check mechanism is less than a predetermined value, while the wall of the recess forms a surface for sliding contact with the piston when this difference in pressure is greater than this predetermined value.

TECHNICAL FIELD

The present invention relates to a thermostatic valve comprising anexpandable-material thermostatic element that is suitable forcontrolling the movements of a check mechanism for regulating thepassage of a fluid through the valve.

BACKGROUND TO THE INVENTION

In numerous applications in the field of fluids, in particular forcooling heat engines, valves of this type are used for distributing afluid entering various tracts as a function of the characteristics, inparticular the temperature characteristics, of this entering fluid.

In currently used valves, the free end of the piston of the thermostaticelement is often rigidly connected to the check mechanism regulating theflow of the fluid into the valve, such that the distance of the valvefrom its seat is controlled by the development of the temperature of thefluid in which the thermostatic element is immersed.

Some operating conditions of heat engines may cause excessive pressurein the water cooling circuits, whilst the thermostatic valve is notopened by thermal stresses as the temperatures are too low. Thisexcessive pressure may be harmful to some components of the circuit.

U.S. Pat. No. 5,482,010 and EP-A-0 694 681 propose thermo-pressostaticdevices that are intended to prevent excessively high pressure on theside of the check mechanism that is remote from that on which the checkmechanism is connected to the piston of the thermostatic regulationelement. These devices are thus applied only to valves that have atleast three fluid inlet ports and are equipped with two checkmechanisms. Any differences in pressure within the valve, caused by thesimultaneous thermostatic control of the two check mechanisms, are thencorrected by pressostatic regulation of one of the check mechanisms, the“by-pass check mechanism” or “short-circuit check mechanism”, whichconsists in pulling this check mechanism in the opposite direction tothat controlled by the expansion of the wax of the thermostatic element.The valves described in the aforementioned documents do not, on theother hand, have any facilities for regulating an increase in pressureof the fluid around the thermostatic element.

The object of the present invention is to propose a thermostatic valvethat limits the risks of damage in the event of the pressure of thefluid in the valve becoming excessively high, on the side of theregulating check mechanism on which this check mechanism is connected tothe piston of the thermostatic element of the valve.

SUMMARY OF THE INVENTION

For this purpose, the invention relates to a thermostatic valve for acooling circuit, in particular associated with a heat engine, comprisinga main housing which forms an inlet orifice for a fluid and at least oneoutlet orifice for this fluid, a check mechanism that is movablerelative to the housing and is suitable for regulating the passage ofthe fluid between the inlet orifice and the outlet orifice, a seat,which is stationary relative to the housing, for receiving the checkmechanism, and a thermostatic element that is provided with a body,which contains an expandable material, and with a piston that is movablerelative to the body, this body being stationary relative to thehousing. The valve according to the invention comprises further aconnecting piece between the check mechanism and the piston, whichconnecting piece is integral with the check mechanism and delimits ablind recess for receiving the piston, the base of the recess forming astop for the piston when the difference in pressure on either side ofthe check mechanism is less than a predetermined value, thus connectingthe check mechanism and the piston to each other kinematically, whilethe wall of the recess forms a surface for sliding contact with thepiston when this difference in pressure is greater than saidpredetermined value, thus allowing the check mechanism to be displacedrelative to the piston, in the displacement direction of the piston.

When the pressure on the side of the check mechanism on which this checkmechanism is connected to the piston of the thermostatic element becomestoo great relative to the pressure on the other side of the checkmechanism, the connecting piece and, as a result, the check mechanismslide so as to distance the check mechanism from its seat, facilitatingor increasing the flow of the fluid into the valve. When this pressuredifferential falls back to a level that is tolerated by the valve,resilient means may return the check mechanism, and therefore theconnecting piece, toward its seat. If, on the other hand, the pressureconditions of the fluid remain tolerable for the circuits, the movementsof the check mechanism are controlled by the piston of the thermostaticelement, as for the valves of the prior art.

In accordance with other characteristics of this valve, takenindividually or in any of the technically possible combinations:

-   -   the connecting piece is press-fitted into an interior crown of        the check mechanism;    -   the connecting piece is integral with a lower portion of the        check mechanism;    -   the valve comprises a spring for returning the check mechanism        toward the seat, the predetermined pressure value being a        function of the adjustment of this spring;    -   the piston and the connecting piece delimit between them a free        space for communication between the base of the blind recess and        the opening of this recess on the exterior;    -   the free space is partly delimited by a flat portion provided        along the piston;    -   the valve comprises a rigid stirrup, which delimits the seat for        receiving the check mechanism and which is joined to the main        housing, on the one hand, and to the body of the thermostatic        element, on the other hand;    -   the valve comprises a secondary housing, which is tightly        connected to the main housing in the region of one of its inlet        or outlet orifices, tightening a flange for connecting the        stirrup;    -   the valve comprises a lid, which is tightly connected to the        main housing and is suitable for connecting a flange of the        stirrup to the main housing;    -   the body of the thermostatic element is arranged in the main        housing, on the flow path of the fluid between the inlet orifice        for this fluid and at least one of the outlet orifices for this        fluid;    -   the main housing delimits a tract for the circulation of a fluid        other than that which is regulated by the check mechanism, the        body of the thermostatic element being arranged in the main        housing, on the path of this other fluid; and    -   the valve comprises both electrical heating means, which        comprise a sheath that is at least partially immersed in the        expandable material of the thermostatic element and a heating        resistor that is accommodated in the sheath and is suitable for        being connected to an electric power supply, and an added        electrical connecting socket, which is suitable for positioning        electrical connecting contacts of the heating resistor and is        tightly joined to the sheath such that the thermostatic        assembly, including the thermostatic element, the heating means        and the electrical connecting socket, is in a pre-assembled        configuration in which this assembly is capable of being fitted        in one piece in the main housing.

BRIEF DESCRIPTION OF DRAWINGS

A better understanding of the invention will be facilitated by thefollowing description, which is given solely by way of example andrefers to the drawings, in which:

FIG. 1 is a schematic longitudinal section of a conventionalelectrically controlled thermostatic element;

FIG. 2 is a view of a thermostatic element to which an electricalconnecting socket has been added, in the region of the ringed detailmarked II in FIG. 1;

FIG. 3 is a plan view along the arrow III marked in FIG. 2;

FIG. 4 is a schematic longitudinal section of a thermostatic valveaccording to the invention, equipped with the thermostatic element andthe socket from FIG. 2;

FIG. 5 is a larger-scale view of the ringed detail marked v in FIG. 4;

FIG. 6 is a section taken along the plane VI-VI marked in FIG. 5;

FIG. 7 is a larger-scale view of the ringed detail marked VII in FIG. 4;

FIG. 8 is a section taken along the plane VIII-VIII marked in FIG. 7;

FIG. 9 is a similar view to FIG. 7, the valve being shown in a differentoperating state; and

FIGS. 10 to 14 are similar views to FIG. 4, respectively showingvariants of the thermostatic valve.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a known thermostatic element, which has the referencenumeral 1 and is intended to be immersed into a fluid of variabletemperature.

The thermostatic element 1 substantially comprises a body 2, which ismade of a readily heat-conducting material, such as a metallic material,for example, and a piston 3, in the form of a rod that is movablerelative to the body 2. The body 2 delimits on the inside anexpandable-type reception cavity 4, which is generally made of wax andis tightly confined by an elastomer membrane 5, which is held firmlyrelative to the body 2 by a lid 6.

When the temperature of the fluid in which the thermostatic element 1 isimmersed increases, the expansion of the wax 4 causes the piston 3 to bepulled in the longitudinal direction X-X of the thermostatic element.When the wax contracts, returning means (not shown) are generallyprovided in order to bring the piston 3 back inside the body 2.

Electrical heating means 8 are provided to facilitate control inconjunction with or independently of the temperature of the fluid inwhich the thermostatic element 1 is immersed. The electrical heatingmeans 8 are in the form of a rigid sheath 9 that passes right throughthe base of the body 2, which is remote from the lid 6, and arepartially immersed in the wax 4. An electrical heating resistor, onlythe electrical connecting contacts 10 of which are visible in FIG. 1A,is accommodated inside the sheath. It will be understood that when theheating resistor is supplied with current, the wax 4 dilates and thepiston 3 is displaced.

FIGS. 2 and 3 show an electrical connecting socket 12.

The socket 12 is in the form of a single-piece component, which isobtained, for example, by moulding a plastics material, and which has asubstantially tubular shape, the longitudinal axis of which issubstantially coaxial to the longitudinal axis X-X of the thermostaticelement 1 when the socket is added to this element.

For this purpose, in this embodiment, the free end of the sheath 9 formsan annular collar 14, which is received in an annular groove 16 formedin the interior wall of the socket 12. A seal 18, fitted in a compressedstate, is inserted between the collar and the socket.

The electrical connecting contacts 10 of the heating resistor, which isaccommodated in the sheath 9, pass right through the seal 18, such thatthese contacts are arranged in the inside volume V₁₂ of the socket. Thecontacts are positioned on either side of an interior support 20, whichis formed by the socket 12. The support 20 extends longitudinally in adiametrical plane of the socket 12, connecting the diametrically opposedinterior wall portions, as shown in FIG. 3. A groove 22 for receivingthe electrical connecting contacts 10 is formed in each side of thesupport 20, the profile of these grooves 22 being suitable for holdingthe contacts, owing to the complementary nature of their shapes.

FIG. 4 shows a thermostatic valve 30 that is suitable for equipping acooling circuit, in particular for the heat engine of a motor vehicle.This valve comprises a main housing 32 delimiting an orifice 33, in theregion of which a secondary housing 34 is added in a tight manner. Thehousing 32 delimits three conduits, having the reference numerals 36, 38and 40. The secondary housing delimits a single conduit, having thereference numeral 42. For example, if the valve 30 is used in a coolingcircuit of a heat engine, the conduit 36 corresponds to a cold-waterinlet that is intended to communicate, under some conditions explainedbelow, and through the orifice 33, with the conduit 42, which forms acold-water outlet in the direction of a heat exchanger; the conduit 38,for its part, forms an inlet for oil circulating in another tract of thecooling circuit, which inlet communicates freely with the conduit 40,which forms an outlet for this oil.

The valve 30 is equipped with means for regulating the flow rate ofwater passing from the inlet conduit 36 to the outlet conduit 42 via theorifice 33, in the form of a closing check mechanism 44 associated witha corresponding seat 46. The check mechanism 44 is adapted to move awayfrom or toward the seat 46, such that when the check mechanism bearsagainst its seat, the flow rate of fluid passing from the conduit 36 tothe conduit 42 is substantially zero, and when the check mechanism 44 isset completely apart from the seat 46, the fluid feeding the conduit 36passes virtually unimpeded into the outlet conduit 42.

In order to control the displacement of the check mechanism 44 relativeto the seat 46, the valve 30 is equipped with the thermostatic element1, to which the connecting socket 12 is added. A major portion of thebody 2 of the thermostatic element 1 is placed in the flow of oilcirculating from the inlet conduit 38 to the outlet conduit 40, whilethe remainder of the body 2 is received in an orifice 47 formed in thewall of the housing 32 separating the water conduit 36 from the oilconduits 38 and 40. The transverse section of the orifice 47 issubstantially complementary to that of the body 2, and sealing means 48arranged around the body 2 prevent any fluid communication between theoil tract and the water tract.

In order to supply the heating resistor of the means 8 with electricpower and mechanically to maintain the connecting socket 12 and thesheath 9 of the thermostatic element 1, which is connected thereopposite the housing 32, a connector 50 is tightly fixed in acomplementary aperture 52 of the housing 32, which extends along thelongitudinal axis X-X of the thermostatic element. In its portion turnedtoward the exterior of the housing, the connector 50 is provided with acavity 54 for receiving an electrical power plug. In its oppositeportion, the connector 50 caps the connecting socket 12, as shown ingreater detail in FIGS. 5 and 6.

More precisely, the connector 50 forms a recess 56 for partiallyreceiving the connecting socket 12, an annular seal 58 being insertedbetween the exterior face of the socket and the wall of the connectordelimiting this recess. The connector 50 is equipped with a plurality offlexible tongue 60 for connecting the socket, distributed over itsperiphery. These tongues are adapted to engage with a rigid annularinsert 62, which is held axially relative to the socket in acorresponding peripheral groove (see FIG. 2) that is provided in theexterior wall of the socket.

A pair of electrical conductors 66, which extend from the cavity 54 forreceiving an electrical power plug up to the recess 56 for receiving thesocket, forming inside this recess resilient conductive pins 68 that areadapted to enter into contact with the contacts 10 of the heatingresistor when the connector is fixed to the socket 12, runlongitudinally along the connector 50.

The piston 3 of the thermostatic element 1 is, for its part, connectedto the check mechanism 44 of the valve 30 via a connecting piece 70. Asshown in greater detail in FIG. 7, the part 70 is connected intranslation along the axis X-X to an interior crown 72 of the checkmechanism 44. The part 70 is, for example, press-fitted into this crown.The part 70 and the check mechanism 44 are therefore connectedkinematically to each other.

In its common portion, the part 70 has a blind hole 74 that is coaxialto the axis X-X and is adapted to receive the rod forming the piston 3of the thermostatic element 1. The free end of the piston is adapted tobear against the base 74 a of the hole 74, so as to facilitate thetransmission, between this piston and the connecting piece 70, of astress along the axis X-X, directed away from the body 2.

As shown in FIG. 8, the piston 3 has a flat portion 76, which, togetherwith the wall 74 b of the hole 74, delimits a free space (referencenumeral 78) that extends up to the free end of the piston. The contactbetween the piston 3 and the wall 74 b is provided in a sliding manner,such that there is a degree of freedom in translation along the axisX-X, between the piston and the part 70. In particular, when thepressure in the water inlet conduit 36 is greater than that in theoutlet conduit 40 by a predetermined value, the pressure differentialexerted on the part 70 is able to cause said part to slide relative tothe piston, said piston guiding the movement of the part 70. In thisconfiguration, shown in FIG. 9, a clearance (J) forms between the baseof the hole 74 and the free end of the piston 3. The free space 78provided in the flat portion 76 then allows fluid to be freelyintroduced into the clearance (J) thus formed, and prevents the part 70from becoming immobilised by a suction effect on the piston 3 in theconfiguration of FIG. 7.

The valve 30 also comprises a stirrup 80, which delimits the seat 46 andwhich rigidly connects the body 2 of the thermostatic element 1 to themain housing 32 of the valve. More precisely, the stirrup 80 comprisesan annular crown 80A, which defines the seat 46, branches 80B, whichconnect the body of the thermostatic element to the crown 80A, anannular flange 80C, which is held tightly between the housings 32 and34, and branches 80D, which form at their free end supporter planes 80Efor a return spring 82. This spring 82 is inserted between the checkmechanism 44 and the stirrup 80, so as to return this check mechanism toits seat 46.

Between each of the branches 80B, openings allow the fluid to pass fromthe inlet conduit 36 to the zone of the crown 80A. Similarly, thebranches 80D define between them orifices allowing the fluid to passfrom the zone of the crown 80A toward the outlet conduit 40, when thecheck mechanism 44 is set apart from the seat 46.

The valve 30 is assembled as follows:

Firstly, the connector 50 is joined to the housing 32 by being broughtfrom outside the housing 32 into the aperture 52. The connector isjoined to the housing in a tight manner by adhesion, by press-fitting orby clamping, for example.

The thermostatic assembly, formed by the thermostatic element 1 and theconnecting socket 12 provided with the insert 62, and equipped with thecheck mechanism 44, the stirrup 80 and the spring 82, is then introducedinto the housing 32, through the orifice 33. The connecting socket andthe body 2 of the thermostatic element are introduced into the orifice47 in a movement of translation along the axis X-X, until the free endsof the branches 80B compress the sealing means 48. The tongues 60 thenengage with the insert 62 of the socket 12, and the pins 68 enter intoelectrical contact with the contacts 10.

The secondary housing 34 is then joined in a tight manner to the mainhousing 32, thus locking the flange 80C of the stirrup 80.

The fact that the electrical connecting socket is added to thethermostatic element before it is fitted in the valve allows apre-assembled thermostatic assembly to be obtained that is easy tointroduce into the housing 32, no supplementary connection process beingrequired in order to hold or position the connecting contacts of theelectrical heating means relative to the housing. Moreover, theelectrical components of the assembly are insulated, at least in part,before the assembly is fitted in the valve, and the insulation maytherefore be tested prior to fitting. The connector 50 cooperates withthe socket 12, to enable the thermostatic element to be supplied withelectric power from outside the housing. The connector is easy toinstall, allowing the connecting contacts held by the socket to beelectrically connected in a single step during the fitting of thepre-assembled assembly, whilst at the same time ensuring completetightness of the socket.

During operation, an oil tract, which enters via the conduit 38 andexits via the conduit 40, and a water tract, which enters via theconduit 36 and which may, depending on the operating conditions of thevalve, exit via the conduit 40, run along the valve 30. First of all, itshall be assumed that the valve 30 is in the configuration shown in FIG.4, i.e. with the check mechanism 44 bearing tightly on the seat 46.

When the temperature of the oil increases, the wax 4 contained in thebody 2 of the thermostatic element 1 dilates, which causes the piston 3to become displaced. Said piston then pulls the connecting piece 70, andtherefore the check mechanism 44, in translation along the axis X-X. Theconduits 36 and 42 are then set in communication. When the temperatureof the oil decreases, the spring 82 returns the check mechanism 44against its seat 46.

An electrical energy source, which is connected to the connector 50 viaits cavity 54 for receiving a plug, may be controlled, independently orin conjunction with the temperature stress generated by the oil, inorder to supply the heating resistor of the heating means 8 of thethermostatic element 1. Thus, once the contacts 10 have been suppliedwith electric power, the wax 4 dilates and causes the conduits 36 and 42to be set in communication with each other, as above.

Furthermore, when the pressure in the inlet conduit 36 is greater thanthe pressure in the outlet conduit 40 by a predetermined value, as afunction, in particular, of the adjustment of the spring 82, thepressure differential causes the part 70, which then slides along thepiston 3, pulling the check mechanism 44, to be pulled in translation,which sets the conduits 36 and 42 in communication with each other. Thevalve 30 thus prevents any damage to the water circuit resulting fromexcessive pressure.

In other words, the check mechanism 44 performs a thermo-pressostaticfunction, as illustrated in FIG. 9.

The flat portion 76 prevents both the production of a clearance (J) ifthere is insufficient pressure between the part 70 ad the piston 3,which might limit by a suction effect the freedom of the part to slidealong the piston, and the trapping of fluid in the clearance (J), whichmight prevent the piston from being returned rapidly and completely tothe base of the hole 74 when the spring 82 returns the check mechanism44, once the pressure differential has dropped back below thepredetermined threshold value.

FIG. 10 shows a variant of the valve 30 that differs substantially fromthe valve of FIG. 4 owing to the shape of its main housing 32. Said mainhousing forms the conduits 36, 38, 40 and 42 in a single piece. In orderto facilitate the installation of the thermostatic assembly comprisingthe element 1 and the socket 12, equipped with the check mechanism 44and the stirrup 80, the wall of the housing that is remote from theaperture 52 has an aperture 86 that is substantially coaxial to theaperture 52. A lid 88 is also provided in order to close the aperture 86in a tight manner, and in order mechanically to hold the flange 80Crelative to the housing 32.

FIGS. 11 to 14 show other variants of thermostatic valves according tothe invention, having the reference numerals 130, 230, 330 and 430,respectively, the elements that these valves have in common with thoseof the valve 30 from FIG. 4 having the same reference numerals,increased by 100, 200, 300 and 400, respectively. The valve 130 fromFIG. 11 differs substantially from the valve 30 owing to the fact thatthere is no electrical control of the thermostatic element 1. Also, theelement 101 is controlled solely by the temperature of the fluid, inparticular oil, tract circulating in the conduits 138 and 140.

The valve 230 from FIG. 12 differs substantially from the valve 30 owingto the fact that the thermostatic element 201 is not controlled by thetemperature of the fluid in which the body 202 of the element might beimmersed. The movements of the piston 203 are therefore controlledsolely by the heating means 208, i.e. they are controlled electricallyfrom outside the valve. Moreover, the connector 250 is held mechanicallyonly by the socket 212, the connector not being joined to the housing232.

The valve 330 from FIG. 13 differs from the valve 30 from FIG. 4 owingto the fact that the oil inlet and outlet conduits are replaced by asecond water outlet conduit 390, which communicates directly with theinlet conduit 336, the body 302 of the thermostatic element 301 beingimmersed in the flow of the fluid passing from the conduit 336 to theconduit 390. The thermostatic element is therefore controlled by thetemperature of this fluid, and is also controlled electrically from theconnector 350. The valve 330 is, for example, used to distribute thecooling water flow rate at the outlet of a heat engine. The valvedistributes this flow rate between the conduit 342, on the one hand,which is intended to be connected to a cooling radiator, and the conduit390, on the other hand, which is intended to be connected to auxiliaryexchangers, such as a cabin-heating unit heater or an oil/water heatexchanger. The assembly and the operation of the valve 330 aresubstantially similar to those described for the valve 30.

The valve 430 from FIG. 14 differs substantially from the valve 330owing to the fact that there is no electrical control of itsthermostatic element. The element is controlled solely by thetemperature of the water passing through the valve via the conduits 436and 490.

Other configurations and variants of the valves described above are alsoconceivable, in particular by combining in a single valve the productionor assembly details described for various valves. For example, flatportions similar to the flat portion 76 of the piston 3 of the valve 30may be provided for the pistons 103, 203, 303 and 403 of the valves 130,230, 330 and 430.

A variant (not shown) of the valve 30 from FIGS. 1 to 9 consists inproducing the check mechanism 44 and the part 70 in a single piece. Moreprecisely, in this case, the connecting piece 70 is integral with aninterior portion of the check mechanism 44, these elements beingproduced from a one-piece part made of metal or a synthetic material.This variant has the advantage of reducing the number of parts of thevalve, while the embodiment of FIGS. 1 to 9 allows a pre-existing checkmechanism to be used, the interior crown 72 of which may be used as afitting zone, either for the connecting piece 70, as described for thevalve 30, or for the body of a thermostatic element, in other knownvalve configurations.

Another variant (not shown) of the valve 30 from FIGS. 1 to 9 consistsin providing that the blind hole 74, which is delimited in theconnecting piece 70, has an oblong-shaped transverse section, ratherthan a strictly circular one. More generally, the profile, in transversesection, of this hole 74 may be proportioned to receive the piston 44and to allow sliding guiding between the piston and the part 70, whilstat the same time providing, in one or more zones along its contour, aradial clearance between the piston and the wall 74 b of the hole 74, soas to delimit between these elements a free space similar to the space78, i.e. a space facilitating fluid communication between the opening ofthe hole 74 on the exterior and the base 74 a of this hole 74. In thiscase, the presence of the flat portion 76 along the piston 3 is nolonger essential, as this free space prevents the suction effect or thetrapping of fluid in a manner similar to the flat portion 76, asexplained above.

1. Thermostatic valve for a cooling circuit, in particular associatedwith a heat engine, comprising a main housing which forms an inletorifice for a fluid and at least one outlet orifice for this fluid, acheck mechanism that is movable relative to the housing and is suitablefor regulating the passage of the fluid between the inlet orifice andthe outlet orifice, a seat, which is stationary relative to the housing,for receiving the check mechanism, and a thermostatic element that isprovided with a body, which contains an expandable material, and with apiston that is movable relative to the body, said body being stationaryrelative to the housing, wherein said valve comprises a connecting piecebetween the check mechanism and the piston, which connecting piece isintegral with the check mechanism and delimits a blind recess forreceiving the piston, the base of the recess forming a stop for thepiston when the difference in pressure on either side of the checkmechanism is less than a predetermined value, thus connecting the checkmechanism and the piston to each other kinematically, while the wall ofthe recess forms a surface for sliding contact with the piston when thisdifference in pressure is greater than said predetermined value, thusallowing the check mechanism to be displaced relative to the piston, inthe displacement direction of the piston.
 2. Valve according to claim 1,wherein said check mechanism defines an interior crown, and saidconnecting piece is press-fitted into said crown.
 3. Valve according toclaim 1, wherein said connecting piece is integral with an interiorportion of the check mechanism.
 4. Valve according to claim 1, andfurther comprising a spring for returning the check mechanism toward theseat, the predetermined pressure value being a function of theadjustment of this spring.
 5. Valve according to claim 1, wherein thepiston and the connecting piece delimit between them a free space forfluid communication between the base of the blind recess and the openingof this recess on the exterior.
 6. Valve according to claim 5, whereinthe free space is partly delimited by a flat portion provided along thepiston.
 7. Valve according to claim 1, and further comprising a rigidstirrup, which delimits the seat for receiving the check mechanism, andwhich is joined to the main housing, on the one hand, and to the body ofthe thermostatic element, on the other hand.
 8. Valve according to claim7, and further comprising a secondary housing, which is tightlyconnected to the main housing in the region of one of its inlet oroutlet orifices, tightening a flange for connecting the stirrup. 9.Valve according to claim 7, and further comprising a lid, which istightly connected to the main housing and is suitable for connecting aflange of the stirrup to the main housing.
 10. Valve according to claim1, wherein the body of the thermostatic element is arranged in the mainhousing, on the flow path of the fluid between the inlet orifice of thisfluid and at least one of the outlet orifices of this fluid.
 11. Valveaccording to claim 1, wherein the main housing delimits a tract for thecirculation of a fluid other than that which is regulated by the checkmechanism, the body of the thermostatic element being arranged in themain housing, on the path of this other fluid.
 12. Valve according toclaim 1, and further comprising both electrical heating means, whichcomprise a sheath that is at least partially immersed in the expandablematerial of the thermostatic element and a heating resistor that isaccommodated in the sheath and is suitable for being connected to anelectric power supply, and an added electrical connecting socket, whichis suitable for positioning electrical connecting contacts of theheating resistor and is tightly joined to the sheath such that thethermostatic assembly, including the thermostatic element, the heatingmeans and the electrical connecting socket, is in a pre-assembledconfiguration in which this assembly is capable of being fitted in onepiece in the main housing.